Grades and specification
VLSFO — very low sulphur fuel oil, maximum 0.50% sulphur, the mainstream compliant marine residual grade.
HSFO — high sulphur fuel oil, typically 3.5% sulphur, used by vessels with exhaust gas cleaning systems.
MGO — marine gasoil, a distillate grade with low sulphur and better cold-flow properties than residual fuel.
ULSFO — ultra low sulphur fuel oil, generally 0.10% sulphur, used in emission control areas.
ISO 8217 — the international specification standard that defines the parameters a marine fuel grade must meet.
Delivery and documentation
BDN — bunker delivery note, the document recording quantity, grade and sulphur content of a delivery.
MFM — mass flow meter, an instrument that measures delivered mass directly and has substantially reduced quantity disputes where mandated.
Ex-wharf — fuel taken by the buyer at the terminal rather than delivered alongside by barge.
Nomination — the formal instruction confirming vessel, quantity, grade, window and delivery location.
Quality issues
Compatibility — whether two fuels can be mixed without precipitating asphaltenes; a live concern with blended VLSFO.
Stability — a fuel's ability to remain homogeneous in storage without separating.
Off-spec — a delivery that fails one or more contracted specification parameters, triggering a claim process.
Cat fines — catalytic fines, abrasive particles that can cause engine wear if not removed by purification.
Commercial terms
Differential — the premium or discount to a published index at which physical fuel is transacted.
Spot vs term — one-off delivery against an ongoing supply agreement with agreed pricing mechanics.
Credit line — the exposure a supplier will carry for a buyer, often the binding constraint on where a vessel can bunker.